1. Field of the Invention
The invention is in the field of material handling and conveying systems.
2. Brief Description of the Background Art
Plate-like workpieces, such as sheets of cardboard or flat folded boxes are emitted from production machines, such as printers or folder-gluers. These articles are usually conveyed from the production machines, counted, stacked, and strapped for handling and shipment to the customer. There are two common methods of accomplishing these operations the shingle-output delivery system and the counter-ejector delivery system.
In a counter-ejector delivery system, such as disclosed in U.S. Pat. No. 5,545,001, issued Aug. 13, 1996 and incorporated herein by reference, the workpieces are counted and stacked as they emerge from the production machine and are ejected as a series of counted stacks onto a conveyor belt that carries the stacks to the work station, where they are strapped for shipment. The counter-ejector system is of particular applicability to workpieces that are of the same thickness at the leading and trailing edge. Such workpieces stack evenly.
In the cardboard box industry, there are a number of widely used box styles that only require side-to-side folds for the gluing needed before shipment as flat boxes. Such boxes include the standard RSC boxes and can be produced by standard folder-gluers, that only fold in the lateral direction, producing boxes that are the same thickness at their leading and trailing edges. Since the counter-ejector mechanism can be designed to operate with a very short cycle time and high through-put, the production rate limiter is usually the production machine and high speed RSC box production machines are usually supplied with counter-ejector delivery systems.
In the shingled-output system, the workpieces fall onto a conveyor belt as they emerge from the production machine. The belt velocity is such that as a workpiece falls onto the belt, its leading edge falls on the trailing edge of the preceding workpiece, producing an overlapping (shingled) stream of workpieces. The belt carries this stream of workpieces to a work station, where they are counted, stacked and strapped. This can be done manually or through a combination of manual and mechanized operations. The shingle-output system is of particular applicability to workpieces that differ in thickness between the leading and trailing edges. When stacked, such thickness differences accumulate, producing lopsided stacks. It is common to compensate for this thickness difference by reversing the orientation of half of each stack. This is usually a manual operation. However, mechanical methods of varying complexity for performing this finction have been developed (See, for example, U.S. Pat. No. 4,784,558, issued Nov. 15, 1988).
There are many box styles (See, for example, U.S. Pat. No. 4,658,961, issued Apr. 21, 1987) that require complex folding operations. The equipment used to fabricate such boxes is referred to as a specialty folder-gluer. Many such box styles in the folded state have a different number of cardboard thickness at the leading and trailing edge, usually requiring handling by a shingle-output delivery system. It is common, in the box industry, to provide specialty folder-gluers with shingle-output delivery systems. In these systems, the stacking and assembly operations described above are usually the limiting factor on the machine's production rate. However, some complex box styles produced by specialty folder-gluers are symmetric from front to back and could be handled by the faster counter-ejector system.
Thus, there is a need, particularly in the cardboard box industry, for a way to combine the production speed of the counter-ejector delivery system with a versatile production machine, such as the specialty folder-gluer.